Reaction injection molding (RIM) is a versatile process by which elastomeric and thermoset parts can be fabricated. The RIM process involves high pressure impingement mixing of a polyisocyanate stream (A-side) and an active hydrogen containing, isocyanate-reactive stream (B-side) followed by immediate injection into the closed mold. The primary appeal of this process lies in its inherently high productivity. One factor which limits productivity, however, is the necessity to spray the molds with external mold release prior to each injection. This is a time consuming task and often has a negative environmental impact. This difficulty can be overcome by the incorporation of an internal release agent into the formulation via one of the two streams which significantly increases the number of molding cycles which can be accomplished between external mold release sprayings. While the internal mold release (IMR) approach is commercially applied, there remain significant shortcomings in the currently available internal mold release systems. The amine-solubilized metallic soaps, which are most commonly used in this application, have been implicated in reduced flowability and increased heat sags for the RIM elastomers in which they are used. Furthermore, the high melting points and limited solubilities of the metallic soaps makes them prone to precipitation in the RIM processing equipment, necessitating regular replacement of the piping.
Liquid IMR agents, particularly silicone fluids, have been investigated previously. Unfunctionalized polydimethylsiloxane fluids are unacceptable because they destabilize air nucleation on the B-side and cause painting problems. Carboxylic acid functionalized silicones have been described which alleviate some of the above limitations (U.S. Pat. No. 4,076,695), but cause serious reactivity problems with the polyurethane formation. Salts formed by the neutralization of tertiary amines with fatty acids have been disclosed (U.S. Pat. No. 4,098,731) as IMR for integral-skin urethane foams. Similarly, salts of primary amines are disclosed in U.S. Pat. No. 3,726,952. The equilibrium concentration of free carboxylic acids in such a salt of a relatively weak acid with a relatively weak basic amine is sufficient to cause reactivity problems similar to those observed in the acidic silicones.
U.S. Pat. No. 4,220,727 discloses aralkyl quaternary aninonium salts as release agents. All of the examples are chloride salts containing at least one "phenyl stearyl" group.
U.S. Pat. No. 4,040,992 discloses the use of N-hydroxyalkyl quaternary ammonium carbonylate salts as catalysts in the production of polyisocyanurates and polyurethanes. Among the exemplary preferred catalysts are N-hydroxypropyl trimethyl ammonium salts of carboxylic acids such as those of formic and acetic acids and of fatty acids such as hexanoic and octanoic acids and the like.